Abstract: Objective To evaluate the effectiveness of the national expanded program on immunization(EPI) among pre-school children in Putuo District. Methods Vaccination rates, adverse reactions and vaccine-related infectious diseases were analyzed among pre-school children before and after EPI implementation. Results A total of 526 children were surveyed after EPI implementation.Vaccination rate reached 95%,adverse reactions rate was 81.44 per 100,000 caes,and the incidence rate of EPI vaccine-related infectious diseases decreased. Conclusion Close cooperation among different departments,full preparation and effective support are the basis of expanded program on immunization.Management should be strengthened of floating children.Surveillance sensitivity of AEFI should be strengthened.And the surveillance of epidemic characteristics of EPI vaccine-related infectious diseases should be strengthened.